Migrationwatch UK insisted the Government's own figures showed the Yorkshire and Humber population had seen a 55,000 net increase due to immigration since 1997, 47,000 of those in the last four years.
The group said the bomb attacks on London were evidence of the failure to integrate immigrants and this could not be achieved unless rates slowed.
The Government described the figures as "highly speculative" while campaigners pointed to the contribution immigrants make.
Migrationwatch UK chairman Sir Andrew Green said: "It seems to us that the really obvious lesson from last July is we have not succeeded in integrating our communities and it is not feasible to do so at the present rate of arrival.
"There is an obvious impact on schools, transport and hospitals but also we are going to need a million new houses in the next 20 years just for immigrants alone. Surely someone should tell us where we are going to put them."
The Migrationwatch UK report said the population had risen on average by 177,000 each year in the past seven years due to immigration.
It also estimated a further 30,000 people had arrived illegally or overstayed their welcome every year.
The Office for National Statistics said the region's population had risen by 81,200 between 1997 and 2004 but was not immediately able to say how much of this rise was down to births, people moving from elsewhere in the country or immigration.
Shadow Home Secretary David Davis, MP for Haltemprice and Howden, said: "Immigration is out of control under Labour.